Jetting Question

[Aussieduner]

My 85/86 Hybrid 250r is still not running correctly,tends to stutter throught the mid range,top end is good
CT Pipe
K&N Filter
Air Box Lid Fitted
160main(have tried 155 with same deal)
Needle 3rd clip
Stock Motor

Any combo's that work ok i can monkey with ?

Aussie

[Jason Hall]

Aussie, start raising the clip on the needle. That will take some of your mid range fuel away.

[Wickedfinger]

Your general altitude, Temp, humidity and plug check color would be helpful please ...... at first guess, I would say Clip position too, but .......

[Aussieduner]

Will do and see how she goes,its giving me the SH#TS having to be on the gas all the time to pass over that stuttering part of the band.

Thanks for the tips gents.

Aussie

[Enigma]

I also have a question about jetting. Would the wrong jet size make it not go back down to idle. I just had my cylinder replated and it runs good but it won't go back down to idle unless I adjust the idle down but then it is too low and it stalls. So I start it up adjust the idle, rev it up and it goes down some but not all the way down. So could it be the jets or something else?

[crackshot]

I fixed all my problems by setting everything (jetting) back to factory spec for my altitute including running 20:1 regular old skool good quality 2 stroke oil.
Running aftermarket expansion chamber and silencer also on a stock engine.
Runs like it should now. Smooth power. Plug is tan like the color of cardboard.

[3Razors]

I also have a question about jetting. Would the wrong jet size make it not go back down to idle. I just had my cylinder replated and it runs good but it won't go back down to idle unless I adjust the idle down but then it is too low and it stalls. So I start it up adjust the idle, rev it up and it goes down some but not all the way down. So could it be the jets or something else?

Maybe your throttle slide might be sticking?

[3Razors]

I fixed all my problems by setting everything (jetting) back to factory spec for my altitute including running 20:1 regular old skool good quality 2 stroke oil.
Running aftermarket expansion chamber and silencer also on a stock engine.
Runs like it should now. Smooth power. Plug is tan like the color of cardboard.

I have a 1985 250r set up the same way. All stock except for a pipe. Runs fantastic on 20:1.

[Wickedfinger]

Maybe your throttle slide might be sticking?
Sounds more likely to be an airleak past the carb somewhere, especially after a rebuild.

[Dammit!]

Aussie, start raising the clip on the needle. That will take some of your mid range fuel away.

I had a similar problem last time out and that's exactly what I did but turned out to be the exact opposite of what I needed to do.

If the machine bogs like you forgot to turn the gas on, drop the clip to raise the needle. It's not getting enough gas.

If it sputters like they do wide open with too rich of a main jet, raise the clip to lean it out.

It's hard to tell the difference until you screw up and adjust the needle in the wrong direction once or twice. :rolleyes:

[TeamGeek6]

If its a PJ, they tend to run very rich from float problems. Mine did exactly the same thing (puked out off idle). The carb (86 PJ) was so whacked I had to ditch the float and use a go kart type fuel control system. Major drop in fuel level and main jet (132). Now it absolutely screams at any throttle setting.

Midrange is made up of:

1.) slow jet
2.) main needle taper, length etc

Changing the main jet wont do much for the midrange, thats (mostly) for wide open.